This invention relates to the manipulation of laser beams for the purpose of materials processing. The laser materials processing techniques that may be performed with this invention include heating, drilling, cutting, cleaning, marking, engraving, welding, transformation hardening, cladding, curing, paint stripping stereolithography, and the general class of laser surface modifications. Each of these laser processes requires that a focused or otherwise shaped laser beam be positioned and/or translated relative to a work surface.
Some laser processes require the laser beam to be stationary with respect to the work surface during processing. In other processes the laser beam is required to travel smoothly along a programmed path on a work surface. Laser cutting is the most common example of this traveling interaction of laser beam and work surface.
The relative motion of laser beam and work surface can be accomplished in a variety of ways depending upon machine floor space, weight, accuracy, ease of work loading, ease of beam alignment, speed of motion, and acceleration along the programmed path.
In high speed laser cutting processes, higher laser power yields higher cutting speed, which cutting speed, in turn, is inversely proportional to the work material thickness. In most laser cutting operations, the cutting speed is limited more by quality and economics than by the ability to manipulate the laser beam along the desired path. In the laser cutting of thin materials, such as cloth or paper, the processing speeds can be very high without sacrificing quality. With thin materials, the laser processing speed is usually limited by mechanical constraints rather than the availability of laser power.
In the so-called "flying optics" approach wherein the laser system is mobile in relation to a stationary work product, the laser beam manipulation offers the fastest travel speed and acceleration. The moving mass of such systems is low since the work holding elements are stationary.
Although the mass of the components within the above systems can be minimized with careful design and advanced materials, the fact that these components must travel along a programmed path rather than a straight path limits higher acceleration and thus limits the average processing speed.
If the laser beam alone can be manipulated along the programmed path, without the limitations of the associated mechanical mass, the lateral acceleration along the path can be increased. "Galvanometer-type" mirror systems such as described within U.S. Pat. No. 4,762,994, entitled "Compact Optical Scanner Driven by a Resonant Galvanometer", for example, are capable of efficient operation at limited laser power. Such systems are typically limited to a laser beam diameter of a few inches, and the beam diameter at the scanning mirror is not large. Galvanometers are not commercially available for manipulating the large diameter laser beams that are required for scanning large surface areas with high power laser beams.
It would be economically advantageous to provide a large diameter laser beam to result in increased laser power directed upon the work surface. The use of the galvanometer-type optical scanner described earlier, requires small-sized mirrors that are incapable of providing such laser beams of increased beam diameter.
Accordingly, it is one purpose of the invention to provide a high power laser system, for focusing and rapidly manipulating a beam focal spot, utilizing larger diameter laser beams and larger mirrors without requiring galvanometer scanners for moving the laser beam relative to the work surface.